Fastrak as used for more than just paying tolls

I recently bought a transponder tag for my car. It's registered with
the state and is associated with my license plate. If I drive through a
toll facility which is suitably equipped, it will automatically subtract
from my balance. When the balance drops too low, it will replenish
itself by applying a charge to my usual payment instrument.

In the Bay Area, this mostly applies to bridges, but there are also a
couple of freeways which have "express lanes" -- lanes where it's free
if you're a carpool, but you have to pay otherwise during rush hour.
Having the transponder mounted on your windshield so it can be read is
how you pay for using those lanes if you're a solo driver. If you're
carpooling, you're supposed to remove it and put it in a little
anti-static bag they supply.

There is at least one other use for these transponders: traffic speed
detection. Some freeway segments have the equipment needed to read the
tags as they pass underneath. If the same ID appears at two known
places a known distance apart in a known amount of time, then
calculating the speed is a simple matter. This isn't particularly
surprising or even new. It's been done in a bunch of places for years.
In San Antonio, the state gave away a whole bunch of these things just
so they'd have more roaming data points on the roads.

For a while, I had a transponder tag for a parking garage on my car. It
was made by the same company who made the tags the state was giving
out. I imagine that every time I drove under one of their readers, it
picked up on the ID and made a note of it. The next time I passed
another reader, it did the math and figured out a speed for that road
segment.

Rejoining the world of tagged vehicles got me thinking about other
potential uses for this technology. Mostly, I started thinking about
how to stop criminals with it. Imagine what would happen if most cars
on the road had some kind of unique identifier which could be
interrogated at a distance. It would open up a whole bunch of
possibilities.

First, realize that probably every car already has a unique ID: the VIN.
You have to get up close and personal to actually read it, though. If
the vehicle is in motion or you otherwise can't get right up to the
windshield, you probably can't read it. There are license plates, but
those can be hard to copy down on the fly, and they can be removed or
changed.

So let's say this exists, and most cars have a transponder tag which has
been added on, or some equivalent device which is part of the built-in
electronics. Now let's say a car is involved in some kind of crime. As
long as there was some kind of listening device which logged it in the
vicinity of the crime at the right time, it can probably be found later.

What's going to do that sort of logging? Easy: other cars. I imagine a
"smart grid" situation in which cars talk to each other and the road
itself. There are already city transit agencies starting to get
licenses for this kind of technology. The magic terms are "5.9 GHz
DSRC".
Look it up - it's fascinating stuff.

Is it such a stretch to think that cars are going to start noticing each
other? I don't think so. Airplanes are already headed in that
direction with
ADS-B. One interesting
point about the ADS-B system is how aircraft learn about each other and
share that data with others. If I'm reading this correctly, plane A can
see plane B and tell plane C about it. C couldn't see B directly,, but
knows of its existence thanks to the report from A. This even applies
if C is using a receive-only "in" system.

It's definitely not a stretch to imagine cars being scanned on purpose
after a crime happens. Police agencies already drive their
"PIPS" cars through an area
where something has occurred. This way, if the bad guys left their car
in the area and later come back to it, there's a log of it being there.
If that same car shows up at yet another crime site later, it can be
correlated.

I've seen my local PD driving up and down the lanes at the big movie
theater parking lot to look for interesting cars. The cameras on top
scan plates as they pass by, and the computer does the rest. They wind
up recovering a bunch of stolen cars this way.

I'm not trying to make dire predictions of a
"grim meathook future"
or anything like that. It just seems likely that such technologies
will be much more closely related not too long from now. It doesn't
even really have to involve law enforcement or their federal buddies.
The nerd contingent could get going on it right now for their own
enjoyment. They're already doing it for ADS-B data with those $20
RTLSDR TV tuner sticks. (Really.)